1. Field of the Invention
The present invention is directed to improve and complete the safety of operation of manually or electrically operated scaffolding winches disposed on suspended scaffoldings for raising or lowering the latter. This invention is applicable notably to scaffoldings, nacelles or similar structures or a portion thereof, of the type suspended from at least two winches secured either to the stirrups of the scaffolding or to an overhead outrigger or cornice hook.
In this case, the winding or unwinding speed of the cable of one of the winches may be greater than that of the other winch, thus causing the scaffolding or like nacelle to cant with respect to the horizontal.
Under these conditions, it is highly desirable to provide some automatic intervention means capable of stopping this canting movement, more particularly in the case of an operation or an accidental coming down occurence.
2. Description of the Prior Art
A device of this character, capable of stopping electric winches, is already known in the art. It consists of a tube disposed horizontally when the scaffolding is in its normal horizontal position, and contains mercury. Since the mercury contained in the tube preserves a horizontal surface irrespective of the tube inclination, the desired result is obtained by means of contacts properly arranged in the tube and connected to electric circuit means controlling the starting and stopping of the winch motors. Now this device is objectionable in that it is applicable only to motorized winches, and is relatively fragile and may even operate untimely as a consequence of jolts produced on the scaffolding.